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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal DOI :
Electronics and Telecommunications Research Institute
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Volume & Issues
Volume 16, Issue 3 - Oct 1994
Volume 16, Issue 2 - Jul 1994
Volume 16, Issue 1 - Apr 1994
Volume 15, Issue 3 - Jan 1994
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A Diffraction Transfer Function Approach to the Calculation of the Transient Field of Acoustic Radiators
Lee, Chan-Kil ;
ETRI Journal, volume 16, issue 1, 1994, Pages 1~1
A computationally-efficient approach to the calculation of the transient field of an acoustic radiator was developed. With this approach, a planar or curved source, radiating either continuous or pulsed waves, is divided into a finite number of shifted and/or rotated versions of an incremental source such that the Fraunhofer approximation holds at each field point. The acoustic field from the incremental source is given by a 2-D spatial Fourier transform. The diffraction transfer function of the entire source can be expressed as a sum of Fraunhofer diffraction pattern of the incremental sources with the appropriate coordinate transformations for the particular geometry of the radiator. For a given spectrum of radiator velocity, the transient field can be computed directly in the frequency domain using the diffraction transfer function. To determine the accuracy of the proposed approach, the impulse response was derived using the inverse Fourier transform. The results obtained agree well with published data obtained using the impulse response approach. The computational efficiency of the proposed method compares favorably to those of the point source method and the impulse response approach.
Analysis of the Generalized Order Statistics Constant False Alarm Rate Detector
Kim, Chang-Joo ; Lee, Hwang-Soo ;
ETRI Journal, volume 16, issue 1, 1994, Pages 17~17
In this paper, we present an architecture of the constant false alarm rate (CFAR) detector called the generalized order statistics (GOS) CFAR detector, which covers various order statistics (OS) and cell-averaging (CA) CFAR detectors as special cases. For the proposed GOS CFAR detector, we obtain unified formulas for the false alarm and detection probabilities. By properly choosing coefficients of the GOS CFAR detector, one can utilize any combination of ordered samples to estimate the background noise level. Thus, if we use a reference window of size N, we can realize
kinds of CFAR processors and obtain their performances from the unified formulas. Some examples are the CA, the OS, the censored mean level, and the trimmed mean CFAR detectors. As an application of the GOS CFAR detector to multiple target detection, we propose an algorithm called the adaptive mean level detector, which censors adaptively the interfering target returns in a reference window.
Input Noise Immunity of Multilayer Perceptrons
Lee, Young-Jik ; Oh, Sang-Hoon ;
ETRI Journal, volume 16, issue 1, 1994, Pages 35~35
In this paper, the robustness of the artificial neural networks to noise is demonstrated with a multilayer perceptron, and the reason of robustness is due to the statistical orthogonality among hidden nodes and its hierarchical information extraction capability. Also, the misclassification probability of a well-trained multilayer perceptron is derived without any linear approximations when the inputs are contaminated with random noises. The misclassification probability for a noisy pattern is shown to be a function of the input pattern, noise variances, the weight matrices, and the nonlinear transformations. The result is verified with a handwritten digit recognition problem, which shows better result than that using linear approximations.
A Study on Modified Silicon Surface after
Reactive Ion Etching
Park, Hyung-Ho ; Kwon, Kwang-Ho ; Lee, Sang-Hwan ; Koak, Byung-Hwa ; Nahm, Sahn ; Lee, Hee-Tae ; Kwon, Oh-Joon ; Cho, Kyoung-Ik ; Kang, Young-Il ;
ETRI Journal, volume 16, issue 1, 1994, Pages 45~45
The effects of reactive ion etching (RIE) of
on the underlying Si surface have been studied by X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometer, Rutherford backscattering spectroscopy, and high resolution transmission electron microscopy. We found that two distinguishable modified layers are formed by RIE : (i) a uniform residue surface layer of 4 nm thickness composed entirely of carbon, fluorine, oxygen, and hydrogen with 9 different kinds of chemical bonds and (ii) a contaminated silicon layer of about 50 nm thickness with carbon and fluorine atoms without any observable crystalline defects. To search the removal condition of the silicon surface residue, we monitored the changes of surface compositions for the etched silicon after various post treatments as rapid thermal anneal,
plasma treatments. XPS analysis revealed that
treatment is most effective. With 10 seconds exposure to
plasma, the fluorocarbon residue film decomposes. The remained fluorine completely disappears after the following wet cleaning.
New N-way Hybrid Power Combiner to Improve the Graceful Degradation Performance
Eom, Soon-Young ; Kim, Jeong-Ho ; Yim, Choon-Sik ;
ETRI Journal, volume 16, issue 1, 1994, Pages 59~58
In this paper, a new N-way hybrid power combiner for improving the graceful degradation performance has been proposed. The proposed combiner has been configured with two dummy transmission lines per each section, where each dummy transmission line has a different characteristic impedance, of the standard combiner. Under this proposed configuration, a detailed theoretical analysis has been performed to show the general function of a power combiner. When any M amplifiers among N identical amplifiers are suffering the failure mode in a power combining circuit or system, the graceful degradation performance has been improved due to the separation of a transmission line and an internal resistor in every failed section from the proposed combiner by simultaneously operating two shorting devices. Simulation results for all the items which can be measured from all the items which can be measured from the proposed combiner with an eight-way configuration have been presented.